Carbon nanotubes, which have various characteristic properties due to their ideal one-dimensional structure such as inelastic electron and spin-conducting characteristics, mechanical strength, light-absorbing and emitting characteristics, heat-conducting property in addition to high electronic conductivity, high electron and hole mobility, are materials having a potential of various industrial applications.
Various production processes such as laser ablation method, chemical vapor-phase deposition method have been known as the methods of producing the carbon nanotube currently. However, it is difficult to control the diameter and length of the carbon nanotube by such conventional methods. Although it is an important technical challenge to place a carbon nanotube at a desired position in a desired direction in application of the carbon nanotube as a part such as electron devices, sensor or wiring, the conventional technology does not give an answer effectively overcoming such problem.
These problems are derived from the fact that metal fine particle catalyst prepared by self structuring and dispersed freely in vapor phase or on a substrate are used as the nucleus for growth in existing carbon nanotube growth methods. The diameter and the growth velocity of carbon nanotube vary significantly, depending on the size and shape of individual catalyst fine particles. As a result, a freely dispersed catalyst inevitably gives rise to a significant variation in growth condition and consequently in the shape, position, and orientation of the formed carbon nanotubes.
It is difficult to control the shape of catalyst metal fine particles at an accuracy of 10 nm or less and the orientation of the growing carbon nanotubes, even when catalyst fine particles are placed on a substrate by patterning in a lithographic process.
However, it is possible to control the shape of graphite structures having a diameter of approximately 100 nm that are significantly larger then common carbon nanotubes. Patent Document 1 and Nonpatent Document 1 disclose the methods of graphitizing a carbon structure due to catalytic effect of iron atoms by heating an amorphous carbon containing iron atoms partially or entirely. It is described that it is possible to produce a polycrystalline graphite structure and also to control the size thereof by the methods.
[Patent Document 1] Japanese Laid-open patent publication No. 2003-238123
[Nonpatent Document 1] J. Fujita, J. Vac. Sci. & Technol. B20, 2686 (2002)